1. Field of the Invention
The present invention relates to a lens holding structure for holding a lens element that is incorporated in an optical instrument such as a camera and the like, and a lens holder for incorporating a lens element in an optical instrument by means of the lens holding structure.
2. Description Related to the Prior Art
Typically, a variety of lens-fitted film units have been popular for the purpose of easily enjoying photography without using ordinary cameras. Such a lens-fitted film unit, after exposure of the maximum number of exposures available on a filmstrip thereof, is simply given to a photofinisher who first removes a film cassette with the filmstrip from the lens-fitted film unit and develops the negatives and then forwards the unit body to the manufacturer for recycling. In recent years, in light of the protection of the environment and the reduction of industrial waste, various efforts are focused on how to increase the ratio of recycling of waste lens-fitted film unit. Unit bodies of the waste lens-fitted film units recovered from photofinishers are disassembled into front and rear covers and base members for recycling by melting them and then forming resin pellets or by cleaning and reusing them as they are after quality examination.
Lens-fitted film units and cheap compact cameras generally include injection-molded resin products for the majority of the parts that are employed for the purpose of cost down. Injection molding, in which a melted resin material is injected into a mold having a cavity in conformity with a product with a high pressure and then cooled and converted into a solid product, is suitable for mass production with an effect of lowering production costs. A taking lens and a lens holder for holding the taking lens that are incorporated in a cheap camera are provided in the form of molded resin products and fixedly installed in the camera by means of fixing claws.
Installing the lens element to the lens holder by means of the fixing claws needs at least one lens retaining member, which is one of causes of hindrance to lowering manufacturing costs. Further, in order to assemble the lens retaining member to the lens holder by means of the fixing claws, the lens holder or the lens retaining member has to be formed with holes for receiving the fixing claws due to structural necessity, which causes a decrease in structural strength of the lens holder and, in consequence, is undesirable in terms of quality. Further, the lens holder is able to thermally deform, so that the lens element is possibly brought into axially unaligned position in high temperature circumstances.
Although it can be thought to eliminate the use of fixing claws for holding a lens element on a lens holder, the lens element that has been caulked to the lens holder once is hardly removable from the lens holder, which makes it hard to reuse the lens element. In order to increase recycling efficiency, it is desirable to employ a number of reusable parts and a lens holding structure that allows the lens element to be easily removed and reused. Further, the conventional lens holding structure possibly causes uneven distribution of holding force exerted on the lens element with an adverse effect of producing deformation of the lens element, which is always undesirable for image quality.
An object of the present invention is to provide a method of lens holding structure which eliminates the necessity of lens retaining member and a method of fixing a lens element to a lens holder by means of the lens holding structure.
Another object of the present invention is to provide a lens holding structure which allows a lens element to be easily disassembled from a lens holder for recycling.
The above objects of the present invention are achieved by a method of fixing a lens element to a plastic lens holder comprising a cylindrical shell having an inner diameter greater than an outer diameter of the lens element, a lens support annular collar formed as an integral part at the bottom of the cylindrical shell for supporting the lens element slipped into the cylindrical shell and a plurality of thermally deformable fixing claws, which comprises the steps of slipping the lens element into the cylindrical shell until the lens element is supported on the lens support annular collar, pressing a heating tool against said fixing claws of the cylindrical shell from a top, and heating and deforming said fixing claws of the cylindrical shell so as to grasp a periphery of the lens element with the deformed parts of the cylindrical shell. The fixing claw is shaped and has a top surface inclined inward up so as to be thermally deformed even with the periphery of the lens element.
The plastic lens holder comprises a cylindrical shell, a lens support annular collar that is integrally formed at a bottom of the cylindrical shell and supports the lens element slipped into the cylindrical shell, and a plurality of fixing claws integrally formed with and axially extending from the cylindrical shell, the fixing claws being arranged in diametrically symmetrical positions with respect to a center axis of the cylindrical shell. The fixing claws are thermally deformed in a radial direction so as to grasp a periphery of the lens element, thereby fixing the lens element to the plastic lens holder. The cylindrical shell may be further provided with a guide wall extending between each adjacent the fixing claws and axially beyond the fixing claw. wherein the guide wall The lens holder may further comprising grooves formed in the cylindrical shell for allowing access of a removing tool to an under side of the lens element for removal of the lens element from the lens holder.